The present invention relates to film cassettes in general, and more particularly to film cassettes for x-ray films. Still more particularly, the present invention relates to film cassettes of synthetic plastic material including two elastically deformable and cylindrically pre-deformed cassette parts which are connected with one another by a hinge, at least one of which is permeable to x-rays, and which are held in their closed position by a latching mechanism.
Film cassettes of this type are already known, for instance, from the German application DE-OS No. 1772040. The cassette disclosed in this publication includes curved aluminum plates which are supported in a frame of synthetic plastic material. It is also contemplated in this publication to use certain synthetic plastic materials for the aforementioned plates, instead of aluminum. The pre-curved plates serve to expel air from the spaces between intensifying shields and the film received therebetween in the course of closing the cassette. In the absence of expulsion of air inclusions, such air inclusions would interrupt the contact of the film with the respective intensifying shield at the location of the air inclusion and this, in turn, would result in foggy or blurred zones of the image formed on the film. A considerable disadvantage of this known x-ray film cassette is that this cassette can be easily bent, twisted or otherwise deformed.
More particularly, owing to the use of the flexible frame of synthetic plastic material in this cassette, the latter would deviate from a plane, for instance, when it is displaced at one of its corners by three to four centimeters. It is also easy to twist or otherwise distort the closed cassette. This problem can be, at least theoretically, overcome by increasing the wall thickness of the two parts of the cassette. However, this is not feasible for reasons of high expenses, high weight, and high x-ray absorption.